Mixture of a polycarbonate and a styrene maleic acid anhydride copolymer

ABSTRACT

Thermoplastic moulding compositions and shaped articles made therefrom of mixtures of A. 5 TO 95 PERCENT BY WEIGHT OF A POLYCARBONATE OF DIVALENT PHENOLS AND B. 95 TO 5 PERCENT BY WEIGHT OF A STYRENE/MALEIC ACID ANHYDRIDE COPOLYMER HAVING IMPROVED STABILITY TO BOILING WATER AND IMPROVED FLOW PROPERTIES.

United States Patent Koehler et al.

[ Jan. 28, 1975 MIXTURE ()F A POLYCARBONATE AND A STYRENE MALEIC ACIDANHYDRIDE COPOLYMER Inventors: Michael Koehler. Vienna, Austria;

Salah Elabd Elghani, Cologne; Richard Prinz, Leverkusen, both of GermanyAssignee: Bayer Aktiengesellschaft,

Leverkusen, Germany Filed: Oct. 25, 1973 Appl. N0.: 409,409

Foreign Application Priority Data [56] References Cited UNITED STATESPATENTS 3,239,582 3/1966 Kcskulu ct u], 260/47 X 3,4625 I5 8/196)C'untrill 3,642,946 2/1972 Gruhuwski 260/873 Primary Examiner-MelvinGoldstein Assistant Examiner-T. Pertilla Attorney, Agent, orFirmConnolly and Hutz [57] ABSTRACT Thermoplastic moulding compositionsand shaped articles made therefrom of mixtures of a. 5 to 95 percent byweight of a polycarbonate of divalent phenols and b. 95 to 5 percent byweight of a styrene/maleic Oct. 28, 1972 Germany 2252974 acid anhydridecopolymer having improved u.s. Cl. 260/873 Stability boflmg water andimproved Int. Cl. C08g 39/10, C08f 41/12 Pmpemes- Field of Search 260/47XA, 873, 93.5 A 5 Claims, 1 Drawing Figure o O 1 40 f 0' M/ /o 2 [A 30 7,2

MIXTURE OF A POLYCARBONATE AND A STYRENE MALEIC ACID ANHYDRIDE COPOLYMERThis invention relates to a thermoplastic moulding compound comprising amixture of polycarbonates of divalent phenols and styrene/maleic acidanhydride copolymers.

lt is known that the properties of polycarbonates, for example theirthermoplasticity, can be modified by the addition of other polymers, butan improvement in one property, e.g. the melt index, is accompanied by adeterioration in other properties (tensile strength, light fastness andresistance to weathering). Polycarbonates have excellent thermal andmechanical properties, but low stability to boiling water; animprovement in their flow characteristics would also be desirable.

This invention relates to thermoplastic moulding compositions whichcomprise or consist of mixtures of a. 5 to 95 percent by weight of apolycarbonate of divalent phenols and b. 95 to 5 percent by weight of astyrene/maleic acid anhydride copolymer.

These moulding compounds have a much greater stability to hot water ascompared to polycarbonates and are substantially improved in their flowproperties. Their mechanical properties are partly improved over thoseof polycarbonates. The high transparency of polycarbonates is preservedin the mixtures. When a solution of a styrene/maleic acid anhydridecopolymer in methylene chloride is added to a polycarbonate solution inthe same solvent, neither cloudiness nor phase separation is observed.These properties of mixtures of styrene/maleic acid anhydride copolymersand polycarbonates are very surprising as polystyrene and polycarbonateare in compatible, i.e. they form cloudy mixtures with poor mechanicalproperties.

The stability of polycarbonates to hot water is increased by theaddition of styrene/maleic acid anhydride copolymers. When standard testbars made from a mixture of parts by weight of styrene/maleic acidanhydride copolymer and 80 parts by weight of polycarbonate are kept inboiling water for 1,000 hours, only one bar breaks in the impactstrength test according to DIN 53 453 whereas when test bars producedfrom pure polycarbonate are subjected to the same conditions, four ofthe bars break (the following were used for comparison: A polycarbonateof 4,4- dihydroxy-diphenyl-propane-(2,2) having a relative viscosity of1.28 determined on a solution of 0.5 g of polycarbonate in 100 ml ofmethylene chloride; a styrene/maleic acid anhydride copolymer, molarratio approximately 88 12, having a relative viscosity of 1.49determined on a solution of 0.5 g of copolymer in 100 ml of methylenechloride). Mixtures of styrene/maleic acid anhydride copolymer andpolycarbonate show an improvement in flow. FIG. 1 shows the flow curvesof several mixtures compared with that of an easily flowingpolycarbonate.

In FIG. I the abscissa indicates the temperature in C at which the flowof the polymer or polymer mixture was determined. The polymer or polymermixture was injection moulded into a die of a bar having a rectangularcross-section of 2 X 20 mm. The die is constructed so that the polymeris introduced in its centre and the bar has the shape of a flat spiral.The length of the bar of polymer obtained (actually it is wound up as aflat spiral) in cm is indicative of the flow properties. This length isgiven in the ordinate of FIG. 1.

The graphs in FIG. 1 show flow properties of various polymer mixtures asfollows:

Graph 1: mixture of 20 percent by weight of a low flow polycarbonate (171.32) and percent by weight of a styrene maleic acid anhydridecopolymer. (closer defined in Example 1) Graph 2: mixture of 50 percentby weight of the same polycarbonate and 50 percent by weight of the samestyrene maleic acid anhydride copolymer.

Graph 3: Mixture of 80 percent by weight of the same polycarbonate and20 percent by weight of the same styrene maleic acid anhydride.

Graph 4: pure polycarbonate, this polycarbonate is different from thepolycarbonate in graphs 1 to 3, a material having very good flowproperties (m -L24) was selected.

The graphs thus show that the flow properties of a polycarbonate havingvery good flow properties as far as polycarbonates are concerned is muchinferior to mixtures of polycarbonates showing low flow and styrenemaleic anhydride copolymers.

Suitable polycarbonates for the mixtures are: highmolecular weightthermoplastic polycarbonates prepared from divalent phenols, e.g.hydroquinone, resorcinol, 4,4-dihydroxy-diphenyl, bis-(4-hydroxyphenyl)-alkanes, -cycloalkanes, -ethers, -sulphides,-sulphones, and-ketones;bisphenols which are halogenated or alkylated in the nucleus;and a, a'-bis-(phydroxyphenyl) -p-diisopropyl benzene. Polycarbonatesbased on 4,4'-dihydroxy-diphenylpropane-(2,2) (bisphenol A),tetrachlorobisphenol A, tetrabromobisphenol A, tetramethylbisphenol Aand trinuclear bisphenols such asa,a-bis(4-hydroxyphenyl-pdiisopropyl)benzene are preferred. They areprepared in known manner by reacting the divalent phenols with aderivative of carbonic acid which forms a polycarbonate.

The molecular weight range of the polycarbonates used is preferably from10,000 to 100,000, most preferably from 20,000 to 60,000, correspondingto a relative viscosity of 1.20 to 1.60 determined on a solution of 0.5gof polycarbonate in ml of methylene chloride at 25C.

The proportions of the two components in the styrene/maleic acidanhydride copolymers may vary within wide limits as may also themolecular weight. The styrene/maleic acid anhydride copolymer cangenerally be prepared by reacting maleic acaid anhydride with styrene atan elevated temperature in the presence of a peroxide catalyst (see US.Pat. Nos. 2,866,771 and 2,971,939). The copolymers may also containa-methyl styrene, vinyl toluene, 2,4-dimethyl styrene, chlorostyrene andother substituted styrenes instead of styrene itself. The molecularweight of the styrene/- maleic acid anhydride copolymers may vary over awide range, e.g. preferably from 2,000 to 300,000 and most preferablywithin the range of about 80,000 to about 200,000. The styrene/maleicacid anhydride copolymer preferably contains between 5 and 50 percent byweight of maleic acid anhydride, more preferably 5 to 30 percent, mostpreferably 8 15 percent. The moulding compounds of this invention can beobtained, for example, by mixing solutions of the two polymer componentsin a suitable solvent or solvent mixture. Additives such as dyes,stabilisers or substances used to achieve special effects may beincorporated in these solutions.

The moulding compositions can then be isolated from these solutions byprecipitation with non-solvents 20C, which corresponds approximately toa molecular weight of 34,000.

EXAMPLE 1 or by evaporation of the solvents. Suitable solvents are, 5Parts of a polyearhohate of 'h y h y' for example, chlorinated,aliphatic hydrocarbons such p p p 'i havlhg a relative VISCOSIW of asmethylene chloride, chloroform and trichloroethand 20 Parts eoholymer f89 p f of y h ane, and halogenated aromatic solvents such as Chloroand l1 Parts of malele e h y having a relahve benzene. The non-solvents usedare preferably alcohols Viscosity of were mlxed m a double Screwextruder such as methanol, ethanol and isopropanol. at 200C, 2500C andand i e Another method of preparing the moulding comPosi- Shapedarticles made from thts mixture are distintions of this inventioncomprises mixing the polymer guished from al'tleles hlade from PPolycarbonate y components in extruders equipped with mixing devices.their improved Stablhty to boiling Water which is When such extrudersare used, the components may Show" as follows: H either all be meltedtogether or the separate melts of 10 Standard test f were Stored mbolhhg Water for the components may be added together, mixed and ex-1,000 hoursthe Impact strength test according to truded DlN 53 453, onlyone of the 10 bars breaks while 4 of The novel moulding compounds areused for making the 10 reference Polycarbonate P bars e shaped articles,e.g. films and threads which are to be The flow Properties of the were lsubjected to prolonged exposure to boiling water. The eomlfared Wlth hof P p ye h moulding compounds may also be used wherever flow chamcalproperties of this moulding composition and properties better than thoseof polycarbonates are those of the following examples are shown In Tablel. quired or wherever styrene/maleic acid anhydride copolymers withimpact strength, notched impact EXAMPLE 2 strength and resistance tocontinuous heat are re- 80 parts of a polycarbonme of 4'4l dihydroxy q II diphenylpropane-(2,2) having a relative viscosity of Parts in thefollowmg pl are'by w'elght and 1.28 and 20 parts of the styrene/maleicacid anhydride ative viscosities throughout this specification aredetercopolymer described in Example 1 are mixed in a mined on solutionsin methylene chloride (0.5 g of subble Screw nd r at 200C, 220C, 250Cand 235C 51111163 in 100 ml of methylene Chloride) at and extruded. Thestability of the product to boiling Preparation of a polycarbonate wateris similar to that in Example 1. The flow proper- 454 parts of4,4'-dihydroxy-diphenyl-2,2-pr0pane ties of the mixture were even betterthan that in Exam- (bisphenol A) and 9.5 parts of p-tertiary-butyLphenoll 1 were suspended in 1.5 litres of water. The oxygen was 5 removed fromthe mixture in a three-necked flask EXAMPLE equipped with a stirrer anda gas inlet tube by mtroducing nitrogen for 15 minutes with stirring.355 parts of 50 parts of the polycarbonate usied m EXafnple l and a 45percent sodium hydroxide solution and 1,000 50 parts f the,styrene/male'c afthydhde copoly parts of methylene chloride were thenadded. The mixmer descnbed m Example are molxed m a gouble ture wascooled to about 25C. This temperature was screw extruder at 220 250 Cand C and maintained by cooling while 237 parts of phosgene f l q TheStablh of.the product to bollmg water is similar to that obtained inExample 2. The flow propwere added over a penod of 2 hours 15 3O mmuteserties of the mixture were even better than in Ex I after the beginningof introduction of phosgene, 75 2 amp 6 parts of a percent sodiumhydroxide solution were 45 added. 1.6 parts of triethylamine were addedto the resulting solution and stirring was then continued for a EXAMPLE4 further 15 minutes. A highly viscous solution was ob- 20 parts f thepolycarbonate used in Example 1 and tained, the viscosity of which wasreduced by the addi- 80 parts f the styrene/maleic acid anhydride wtionofmethylene chloride.The organic phase was then described i Example 1are mixed i a double Separated from the aqueous phase and Washed withscrew extruder at 200C, 220C, 250C and 235C and water until the waterwas free from salts and alkali. The d The impact Strength f the productis practipolycarbonate was isolated from the washed solution llunchanged after 1,000 hours i b ili w Th and dried. It had a relativeviscosity of 1.32 determined flow properties of the mixture were evenbetter than in on a 0.5 percent solution in methylene chloride atExample 3.

Table 1 property: test-method: unit of Example 1: Example 2: Example 3:Example 4:

measure:

impact strength DIN 53453 cmkp/cm 20C not broken not broken not broken21 40C not broken 82 45 21 notched impact DIN 53 453 cmkp/cm strength20C 17 16 19 4 40C 7 DIN 53455 kp/cm 568 575 642 tensile strength Tablel-Continued property: test-method: unit of Example I: Example 2: Example3: Example 4:

measure:

G l.0 elongation DIN 53455 3.3 3.3 3.3

G 1.0 modulus of ela- DIN 53455 kp/cm 25.500 25.000 29.000 32.500

sticity ball indentation DIN 53456 kp/cm 1.220 1.200 l.400 1.685

hardness heat tii s'iii'r'iion DIN 53460 c 144 143 134 126 temperatureaccording to Vicat( I claim: thylbisphenol A or a trinuclea r bisphenol.

1. A thermoplastic moulding composition consisting essentially ofamixture of (a) from 5-95 percent by weight of a polycarbonate of adihydric phenol and a derivative of carbonic acid (b) from 95 to 5percent by weight of a copolymer of styrene and maleic acid anhydridecontaining from 5 to 50 percent by weight of maleic acid anhydride.

2. A moulding composition as claimed in claim 1 in which thepolycarbonate is based on bisphenol A, tetrachlorobisphenol A,tetrabromobisphenol A, tetrame- 3. A composition as claimed in claim 1in which the polycarbonate has a molecular weight of from 10,000 to100,000.

4. A composition as claimed in claim I in which said copolymer has amolecular weight of from 2,000 to 300,000.

5. A composition as claimed in claim 4 in which the copolymer has amolecular weight of from 80,000 to 200,000.

1. A THERMOPLASTIC MOULDING COMPOSITION CONSISTING ESSENTIALLY OF AMIXTURE OF (A) FROM 5-95 PERCENT BY WEIGHT OF A POLYCARBONATE OFADIHYDRIC PHENOL AND A DERIVATIVE OF CARBONIC ACID (B) FROM 95 TO 5PERCENT BY WEIGHT OF A COPOLYMER OF STYRENE AND MALEIC ACID ANHYDRIDECONTAINING FROM 5 TO 50 PERCENT BY WEIGHT OF MALEIC ACID ANHYDRIDE.
 2. Amoulding composition as claimed in claim 1 in which the polycarbonate isbased on bisphenol A, tetrachlorobisphenol A, tetrabromobisphenol A,tetramethylbisphenol A or a trinuclear bisphenol.
 3. A composition asclaimed in claim 1 in which the polycarbonate has a molecular weight offrom 10,000 to 100,000.
 4. A composition as claimed in claim 1 in whichsaid copolymer has a molecular weight of from 2,000 to 300,000.
 5. Acomposition as claimed in claim 4 in which the copolymer has a molecularweight of from 80,000 to 200,000.